Torque converter clutch lockout hydraulic system

ABSTRACT

A system for controlling operation of a bypass clutch for a torque converter in an automatic transmission includes a converter lockout valve for producing a pressure signal having a first magnitude indicating unlocked operation of the converter clutch and a second magnitude representing locked operation, the pressure magnitudes being produced in response to control pressures representing engine speed, transmission operation in any forward gear, and in a first forward gear.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the control system for an automatictransmission, particularly with respect to the control of a torqueconverter bypass clutch.

2. Description of the Prior Art

A hydrokinetic torque converter, which forms a hydrokinetic torque flowpath from the engine crankshaft to the input elements of a gear ring ofan automatic transmission, includes a turbine and an impeller arrangedin a toroidal fluid flow circuit. It includes also a friction bypassclutch adapted to connect the impeller to the turbine to establish amechanical torque flow path in parallel with respect to the hydrokinetictorque flow path of the torque converter.

The hydrokinetic torque converter of our invention includes a bypassclutch controlled by an hydraulic valve system. The bypass clutch hasfeatures that are common to the control system described in U.S. Pat.No. 5,029,087, and the hydrokinetic torque converter control system ofU.S. Pat. No. 5,303,616. These patents are assigned to the assignee ofour present invention. The '087 patent describes a torque convertercontrol system having a lock-up clutch for establishing a controlledmechanical torque flow path between the engine and the transmissiongearing and for modifying the bypass clutch capacity during shiftintervals. That patent discloses an electronic control strategy foreffecting a control slip in a torque converter bypass clutch, wherebythe bypass clutch is actuated by modulated converter clutch solenoidpressure from a clutch solenoid valve to effect varying clutch capacityso that the resulting control slip results in an actual slip thatapproaches a target slip determined by the operating parameters of thedriveline.

The '616 patent describes a torque converter control system having alock-up clutch for establishing a controlled mechanical torque flow pathbetween the engine and transmission gearing and for modifying the bypassclutch capacity during gearshift intervals.

SUMMARY OF THE INVENTION

A purpose of the converter lockout system of this invention is toprohibit engagement of the converter clutch at an inappropriate time,such as when forward or reverse engagements are initiated, yet to permitengagement of the clutch in all forward ranges and at low engine speedswhen the transmission is operating in the second, third, fourth, andfifth gears. Essentially, a lockout valve 130 compares multiplehydraulic pressure control signals and produce a high pressure or lowpressure signal output, which output is applied to a converter regulatorvalve.

In realizing these objects and advantages in a transmission havingmultiple speed ratios, a system for producing a pressure signal whosemagnitude represents locked and unlocked operation of a converterclutch, includes a first source of pressure representing forward driveoperation of the transmission, a second source of pressure representingoperation of the transmission in a first forward speed ratio, a sourceof regulated pressure, and a third source of pressure having a range ofmagnitude that varies in response to engine speed.

A lockout valve produces converter lockout pressure having a firstmagnitude representing a command to unlock the converter by opening aconnection between the source of regulated pressure and said outletport, and a second magnitude representing a command to lock theconverter in response to the effect of the first, second and thirdpressure sources.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, and 1C, in combination, show a schematic diagram of ahydraulic control circuit for an automatic transmission.

FIG. 2 shows the variation of flow rate through a sharp-edged orificeand laminar orifice as temperature changes.

FIG. 3 is a schematic diagram of the ANSI symbols for a relief valvemodified to include a sharp-edged orifice and laminar orifice.

FIG. 4 is a schematic diagram of the ANSI symbols for reducing valvemodified to include a sharp-edged orifice and laminar orifice.

FIG. 5 is a schematic diagram of the microprocessor, sensors, andsolenoid-controlled valves used to control operation of thetransmission.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1A and 1B, the hydraulic system for controlling andactuating components of an automatic transmission for an automotivevehicle includes a sump 10 where hydraulic fluid is contained and fromwhich it is drawn by a scavenge pump 12 and delivered to a reservoir 14.The inlet of a high flow rate pump 16 is connected through check valve18 to the reservoir. The output of pump 16, secondary regulated pressureSRP, is maintained at approximately 120 psig or greater throughoperation of SRP regulator valve 52. The inlet of pump 22 is drawnpartially from reservoir 14 through a supercharging nozzle 24, whichcarries fluid through the system from various components of thetransmission. The outlet of pump 22 in line 24 is maintained atregulated line pressure through control of a pressure signal produced bya variable force solenoid-operated valve 25 and is applied to a clutchcapacity line pressure regulator valve 212.

Torque converter 20 includes a bladed impeller wheel 26, permanentlydriveably connected by an impeller casing 28 to the crankshaft of aninternal combustion engine 30. A bladed turbine wheel 32 and a bladedstator wheel 34 are mounted in relation to the impeller so that theyform a toroidal flow path within which the hydraulic fluid of the torqueconverter circulates and rotates about the axis of the torque converter.Stator wheel 34 is mounted on one-way clutch 36 to provide one-way driveconnection to the transmission casing. A torque converter lockout orbypass clutch 38, when engaged, produces a mechanical drive connectionbetween the turbine and impeller and, when disengaged, permits ahydrokinetic drive connection between the turbine and impeller. Clutch38 is disengaged or unlocked and the torque converter is opened when CBYpressure in line 40 is applied to the space between the impeller casingand the friction surface of clutch 38 that engages casing 28. CBYpressure is greater than CI pressure in line 46. Line 44, at CTpressure, is drained through an oil cooler 126, and CI pressure in line46 is supplied to the torus of the torque converter through orifice 122when clutch 38 is disengaged.

Secondary Regulated Pressure Valve

A temperature compensated, pressure limiting valve 52 produces anoutput, SRPX pressure, carried in line 82 to anti-drain back valve 78,whose output, torque converter feed pressure TCF, is carried in line 88to the converter regulator valve 86. Secondary regulated pressure,controlled by valve 52, is carried through line 54.

Valve 52 includes a spool 56, urged by a spring 58 rightward in thevalve bore, which rightward movement is limited by contact of controllands 60 against the valve body. SRP feedback pressure in line 62 entersthe valve through a sharp edged orifice 64. The radial space betweenlands 60 and the valve bore defines a laminar orifice, which extendsalong the axis of valve 52 from the feedback port, connected throughline 62 to vent port 66. Preferably, the diameter of orifice 64 is 1.0mm, the diameter of lands 60 is 14.994 mm, and the diameter of the boreadjacent lands 60 is 15.019 mm.

Throughout this discussion, a fixed or sharp-edged orifice means aconstricted hydraulic passage, through which the flow rate variesnonlinearly with a pressure drop across the orifice, approximately asthe square root of the pressure drop, and the flow rate variessubstantially linearly with the temperature of fluid, such ascommercially available transmission hydraulic fluid, flowing through theorifice. A laminar orifice means a constricted passage, through whichthe flow rate varies linearly and directly with the pressure drop acrossthe orifice, and exponentially (or logarithmically) with the temperatureof fluid flowing through the orifice.

Valve 52 further includes control lands 68, 70; SRP input port 80, SRPXoutlet port 81; supercharge outlet port 74, connected by line 76 tosupercharge relief valve 78.

Relief valve 52 is normally closed by spring 58, which causes spool 56to move to the right-hand extremity of the valve while the flow ratefrom pump 16 is so low that SRP pressure is relatively low. In thatposition, line 76 is closed by land 68 from SRP line 54, and converterfeed line 82 is closed by land 70 from SRP line 54. Converter feed line82 is connected through orifice 75 to SRP line 54. As the flow rate frompump 16 and SRP pressure rise, control pressure on the right-hand end ofspool 56 first opens SRPX output port 81, thereby connecting SPR line 54to anti-drain back valve 78 through line 82. Pressure SRPX in line 82moves spool 84 of anti-drain back valve 78 leftward, thereby connectingtorque converter feed pressure TCF in line 82 to converter regulatorvalve 86 through line 88. As SRP rises yet further, land 68 throttlesSRP at port 74 so that fluid at SRP is connected to line 76, nozzle 24,check valve 18, and line 144.

The feedback chamber at the right-hand end of the bore of valve 52 isexhausted through a high resistance laminar orifice 60 and is fedthrough a viscosity insensitive fixed orifice 64. At automatictransmission fluid temperatures below 150° F., flow through the laminarorifice is negligible; therefore, the steady-state differential pressureacross the fixed orifice is negligible. At fluid temperatures above 200°F., leakage through laminar orifice 60 increases. In this manner, apressure divider is established, and the feedback pressure flow throughvalve 52 is thereby reduced as temperature rises above 200° F. inproportion to the hydraulic resistance values of the two orifices 60,64.

Converter Regulator Valve

Converter clutch regulator valve 86 controls three modes of operation:clutch disengaged or open converter operation; clutch engaged or hardlocked converter operation; and modulated slip or partial engagement ofthe torque converter clutch 38. A variable pressure signal TCC iscarried in line 90 to the right-hand end of valve 86 from a converterclutch solenoid-operated valve 92. The magnitude of this pressure signalis proportional to a predetermined clutch torque capacity and a pulsewidth modulated PWM duty cycle control signal produced by amicroprocessor and applied to the solenoid of valve 92. Valve 86modulates differential pressure across the friction surfaces of clutch38 in proportion to the TCC commanded pressure.

Valve 86 includes a spool 94 moveable within the valve bore and carryingfour control lands 96, 98, 100, and 102. Valve sleeve 104 is fixed inposition in the valve chamber by a retainer, the sleeve supporting abooster spool 106, which is urged by torque converter feed TCF pressurerightward against the left-hand end of spool 94. A vent port 108communicates with the valve chamber and is opened and closed by controlland 102. A compression spring 110 urges spool 94 rightward within thevalve chamber.

Line 88 carries torque converter feed pressure to passage 112, andthrough orifice 114, to the valve bore or chamber. Passages 112, 118,and 120 connect line 88 to the valve chamber at mutually spacedpositions.

Line 40 connects an outlet port of valve 86 to the passage through whichclutch 38 is disengaged. Line 44 connects the return line from thetorque converter directly to torque converter exhaust line 113, 114, andthrough lines 116, 119, which are connected to the ports of valve 86.Line 46 carries fluid at converter feed pressure to torque converter 20through valve 86.

The torque converter 20 is opened, i.e., bypass clutch 38 is disengaged,when the PWM duty cycle supplied to the solenoid of the converter clutchsolenoid-operated valve 92 is zero, thereby reducing pressure to zero inline 90 and at the right-hand end of spool 94. In this instance, torqueconverter feed pressure operating at the left-hand end of spool 106forces spool 94 to the right-hand extremity of the valve chamber. Inthis position, valve 86 connects line 118 to line 40, therebypressurizing the space between impeller cover 28 and the frictionsurface of clutch 38. Valve 86 connects line 120 through orifice 122 toline 46, through which hydraulic fluid is delivered to the torus of thetorque converter. Fluid at the exit of the torus, carried in line 44,enters the valve chamber through lines 116, 119, and is carried inconverter exhaust TCX line 113 to oil cooler 126 through superchargedrain back valve 78. Spool 84 of valve 78 will have moved to theleft-hand end of its chamber against the effect of the compressionspring due to the presence of SRPX pressure at the right-hand end ofspool 84, as has been described above with reference to the operation ofthe valve 52.

A 1-2 shift valve 200 connects a source of regulated line pressure 1X toline 128 whenever the first gear ratio is selected. A lubricationaugmentation and converter lockout valve 130 includes a spool 132, whichmoves leftward within the valve chamber due to the effect of compressionspring 134 and a pressure force developed on land 136 when line 128 ispressurized. With valve 130 in this position, fluid at SRP, carried inline 54 from valve 52 and through line 138 to the converter lockoutvalve 130, is connected through valve 130 to an UNLOCK line 140, whichis connected to the chamber of the converter regulator valve 86 at aport located between spools 106 and 94.

When lines 140 and 88 are pressurized, there is no differential pressureacross spool 106, and spool 94 is moved to the right-hand extremity ofthe valve chamber due to a pressure force applied to the large pressurearea on the left-hand end of land 102. This action moves spool 94rightward to the same position as previously described with respect toopen torque converter operation. In this condition, torque converterclutch 38 is disengaged and the torque converter 20 operates in an opencondition. In this way, valve 86 provides an independent override orlockout force on the large diameter of land 102 to ensure that thevehicle can be started and driven in first gear with the converter open,even if an obstruction is present at a port of valve 86, whichobstruction might otherwise prevent spool 94 from sliding to theright-hand end of the valve chamber. This lockout or override featurealso permits the torque converter to operate in an open condition evenif a failure of solenoid 92 or the microprocessor control system wouldcause pressure in line 90 to be high. Low pressure in line 90 would beexpected during normal operation, as mentioned above. In that case, SRPpressure operating on a larger land on the left-hand side of spool 94overcomes the effect of the pressure present in line 90 and permitsspool 94 to move to the open condition at the right-hand end of thechamber. This prevents stalling of the engine in reverse gear or driveconditions in the low gear ratio.

To operate the torque converter 20 in the locked condition, clutch 38 isengaged due to the presence of a larger pressure in the torque converterthan the pressure in the space between the impeller casing and thefriction surfaces of clutch 38. The torque converter operates in thelocked condition when solenoid-operated valve 92 produces a pressure ofabout 50 psig in line 90, thereby moving spool 94 to the left-hand endof the valve chamber. Spool 94 moves to the left-hand end of the chamberwhen the UNLOCK pressure line 140 is closed at valve 130 due to theabsence of 1X pressure from the 1-2 shift valve and due to the largerpressure force acting on the right-hand end of land 96 in comparison tothe pressure force at the left-hand end of booster 106 produced by TCFpressure. With the valve located at the left-hand end of the chamber,line 88 is connected directly through lines 118, and through line 120and orifice 122 to the torus of the torque converter through line 46.Fluid located between the impeller casing 28 and clutch 38 is exhaustedto reservoir through line 40 and vent port 108, thereby producing adifferential pressure across the friction surfaces of clutch 30 forcingit to the locked or engaged condition. Fluid from the torque converterreturns through line 44 to line 113, which directs torque converterexhaust TCX to cooler 126 through valve 78.

Microprocessor Controller

FIG. 6 shows a microprocessor that is used to control the valve circuitsthat in turn control distribution and exhaust of actuating pressure tothe clutches and brake servos for the transmission. The processor isshown at 170 in FIG. 6.

As schematically represented in FIG. 6, an aircharge temperature sensor172 is adapted to develop and ambient air temperature that is used bythe processor in developing commands issued to the control valve system.The processor also responds to an air conditioning clutch signal fromsensor 174 which indicates whether the air conditioning system is on oroff.

A brake on/off switch 176 is triggered by the vehicle brakes and theon/off signal is delivered to the processor.

An engine speed sensor 178 measures crankshaft speed. Engine coolanttemperature is sensed by temperature sensor 180.

The drive range selected by the operator is indicated by a manual leverposition sensor 182. A transmission output shaft speed sensor 184provides an indication of the driven shaft speed an output shaft. Thatspeed is related to the vehicle speed signal developed by sensor 86. Atransmission oil temperature signal is delivered to the processor bysensor 188. An engine throttle position signal is delivered to theprocessor by sensor 190.

The control valve circuit includes solenoid operated shift valves whichreceive shift signals. These are variable force signals from theprocessor. They are received by shift solenoid 192-195.

The sensor inputs, such as the engine-related sensor signals indicativeof engine coolant temperature, barometric absolute pressure, etc., areused by the processor to develop more accurate outputs as the load andclimate conditions change. Other inputs are based n driver commands suchas the engine throttle position. Still other inputs to the processor aredeveloped by the transmission itself, such as the output shaft speedsensor signal, the manual lever position signal, and the transmissionoil temperature signal. The processor will develop the appropriate shifttime and conditions for shifts in the ratio as well as control theclutch application and release. Line pressure also is developed by theprocessor to establish optimum shift feel.

The processor is an integrated central processor which converts signals,such as the signals from a vehicle speed sensor and an engine throttleposition sensor, engine temperature sensor, turbine speed sensor, andthe manual selector lever, into electrical signals for solenoid-operatedvalves 192-196, the solenoid valve for the converter bypass clutch 92,and the variable force solenoid for the electronic pressure control 25.The processor receives the sensor signals and operates on them inaccordance with programmed control algorithms. The processor includesappropriate gates and driver circuits for delivering the output of theoperation of the algorithms to the hydraulic solenoid control valves.

The processor 170 includes a central processor unit (CPU); a read-onlymemory (ROM), in which the control unit that includes a read-writememory or RAM; and internal busses between the memory and the centralprocessor arithmetic logic unit.

The processor executes programs that are obtained from the memory andprovides the appropriate control signals to a valve circuit as the inputsignal conditioning portions of the processor reads the input data andthe computation logic portions deliver the results of the computation tothe output driver system under the program control.

The memory includes both a random access memory (RAM) and a read-onlymemory (ROM), the latter storing the information that comprises thecontrol logic. The result of the computations carried out on the inputdata is stored in RAM where it can be addressed, erased, rewritten orchanged, depending upon the operating conditions of the vehicle.

The data that is stored in ROM memory may be shift schedule informationor functions in which two variables, such as throttle position andvehicle speed, are related one to the other in accordance with a shiftfunction. The data also may be in the form of information in a tablecontaining three variables or data such as a timer value and values forthe other two pieces of data or variables.

The control strategy for the transmission is divided into severalroutines and control modules which are executed sequentially in knownfashion during each background pass. The strategy for each module isexecuted furthermore in sequential fashion, just as the modulesthemselves are executed in sequential fashion. The various dataregisters are initialized as input data from the previously mentionedsensors are introduced into the input signal conditioning portion of theprocessor. The information that results from the inputting of the sensordata, together with information that is stored in memory and learnedfrom a previous background pass, is used to carry out the controlfunctions of the shift solenoid valves, the throttle pressure solenoidvalve, and the bypass clutch solenoid valve. The modules and submodulesare executed in sequence in each background loop. Each module or logicportion is independent of the others and performs a specific function.They are executed as they are separately addressed by the processorpointer. The functions occur after the input signals are received by theinput gates and the signal conditioning portions of the processor andafter the input signal conditioning has occurred.

The ability of the clutches and brakes to transmit torque depends, ofcourse, on the level of the pressure maintained in the control circuitby the main pressure regulator. This control is unlike TV pressurecontrols of conventional transmissions which rely upon mechanicalthrottle valve linkages to maintain a desired throttle valve pressure ora vacuum diaphragm which is actuated by engine intake manifold pressure.The TV control in the present design is achieved by a variable forcesolenoid valve that responds to a signal developed by the electronicmicroprocessor. Electronic TV strategy for the processor includes thestep of looking up engine torque from a table and varying appropriatelythe signal delivered to the variable force solenoid to adjust the torquetransmitting capacity of the transmission.

Converter Lockout Valve

A lube augmentation and converter lockout valve 130 is supplied throughline 128 with 1X pressure from 1-2 shift valve 200, which connects asource of regulated line pressure to line 128 in accordance with controlpressure from solenoid valve 195 when operation in the first forwardgear is required.

Alternatively, line pressure can be directed through line 128 or anotherline from a manual valve 202 when the vehicle operator selects operationin the reverse range.

Supercharge pressure SPS is carried in line 144 to a port located nearthe left-hand end of the chamber of valve 130. Supercharge pressure isregulated by supercharge relief valve 79 at approximately 50 psig and isapplied to a control land of valve 130 that is approximately five timeslarger than the other control lands formed on spool 132, on which otherpressure signals operate to control the position of spool 132. Secondaryregulated pressure SRP is carried in lines 54 and 138 to valve 130.Valve 130 is supplied also through lines 142, 204 with D321 pressurefrom a manual valve 202, which connects a source of regulated linepressure LP in line 24 to line 204 when the manual valve is moved by thevehicle operator's movement of the range selector (PRNDL) to any of theforward drive positions. Absence of D321 pressure is an indication ofreverse drive operation of the transmission, i.e., low pressure in line142 indicates that the vehicle operator has located the PRNDL rangeselector lever in the R-range. Fluid output from valve 130 is carried inline 146 through orifice 148 and filter 152 to various lubricationcircuits 147-150, bypassing a temperature compensated orifice 154 towhich fluid is carried from valve 130 through line 156.

Line 140 carries UNLOCK pressure to a port of valve 86 located betweenbooster spool 106 and land 102 of spool 94. Compression spring 134 urgesspool 132 and the large control lands of spool 206 leftward in the valvechamber.

A purpose of valve 130 is to prohibit engagement of clutch 38 at aninappropriate time, such as when forward or reverse engagements areinitiated, yet to permit engagement of clutch 38 in all forward rangesand at low engine speeds when the transmission is operating in thesecond, third, fourth, and fifth gears. Essentially, lockout valve 130compares three hydraulic pressure signals, D321, 1X, and SPS, andproduce a high pressure or low pressure signal on line 140, which isapplied to the converter regulator valve 86, the high pressure signalrepresenting an UNLOCK control signal.

During conditions when the manual selector is in the park, reverse, orneutral positions, and engine speed is at idle speed or a lower speedthan 2000 rpm, D321, 1X, and SPS pressures are at low magnitude;therefore, spool 132 moves to the left-hand end of the valve chamber,thereby opening a connection between secondary regulator pressure line138 and UNLOCK line 140. The UNLOCK pressure causes the spool 94 of theconverter regulator valve 86 to move to the right-hand end of its valvechamber, thereby opening a connection between torque converter feed line88 and line 40, through which pressure is applied to the space betweenthe impeller cover and the friction surfaces of clutch 38. This actiondisengages the clutch and opens the torque converter.

When the transmission is operating in the D range in first gear atengine idle speed or at engine speed less than 2000 rpm, or in themanually selected first gear ratio with engine speed below 2000 rpm,D321 pressure tends to cause spool 132 to move rightward and 1X pressuretends to move the spool leftward. Therefore, since D321 and 1X pressureare at substantially the same line pressure magnitude and SPS pressureis low, the position of spool 132 is determined by the effect of spring134, thereby opening SRP line 138 to the UNLOCK line 140, and clutch 138is disengaged as described immediately above.

With the transmission operating in the reverse or R-range with enginespeed above 3000 rpm, or in the drive or D-range in first gear withengine speed above 3000 rpm, D321 and 1X pressure have substantiallyequal magnitude and virtually no net effect on the position of spool132. But SPS pressure (approximately 50 psig or greater) operating onlands 206 moves spool 132 rightward against the effect of spring 134..As engine speed rises above 3000 rpm, SPS pressure increases in order tosave power; therefore, the SPS related pressure force on the end of land206 increases and moves spool 132 to the right-hand end of the valvechamber. This action closes communication between SRP line 138 andUNLOCK line 140; therefore, converter regulator valve 86 operates asabove described when UNLOCK pressure is absent from the left-hand end ofspool 94.

With the transmission operating in first gear, either in the manualrange or in the drive range and with engine speed greater thanapproximately 3000 rpm, D321 pressure tends to move spool 132 rightwardand 1X pressure tends to move spool 132 leftward, thereby effectivelycanceling the pressure force acting in the opposite direction caused byD321 pressure at the left-hand end of spool 132. In this case, SPSpressure operates against the effect of spring 134, moves the spool tothe right-hand end of the valve chamber, and closes SRP line 138 toUNLOCK line 140. Therefore, converter regulator valve 86 operates asabove described when UNLOCK pressure is absent from the left-hand end ofspool 94.

With the transmission operating in second gear through fifth gear in thedrive range and with engine speed above 3000 rpm, 1X pressure is absentat the right-hand end of spool 132, D321 pressure is present at theleft-hand end of the spool, and SPS pressure operates on lands 206 tomove spool 132 to the right-hand end of the valve chamber, therebyclosing opening SRP pressure line 138 to UNLOCK line 140.

When the manual gear selector is in the D-range and the transmissionoperates in the second through fifth forward speed ratios with enginespeed in the range 800-1200 rpm, SPS and 1X pressures are low or absentat valve 130, but D321 pressure forces spool 132 against spring 134 tothe right-hand end of the valve chamber, thereby closing the connectionbetween SRP line 138 and UNLOCK line 140. In this position, the TCregulator valve 86 operates as previously described in the absence ofUNLOCK pressure so that the converter clutch is either opened or closedin accordance with the pressure control signals at valve 86. UNLOCK line140 is vented through port 160 when spool 132 moves to the right-handend of its valve chamber.

The flow rate to lubrication circuits 147-150 is relatively low atengine idle speeds, but as transmission output shaft speed rises, thelubrication requirement increases. An object of the control strategy isto prevent torque converter lockup when the lubrication requirement islow. To produce this effect, when spool 132 is moved leftward, as it iswhen engine speed and SPS pressure are low, fluid flow through line 156is closed by spool 132 from a connection to line 146, thereby preventingany augmentation of the lube flow through line 146 to the lubricationcircuits 147-150. In this condition, torque converter lockup isprohibited.

However, when engine speed and SPS pressure increase, spool 132 moves tothe right-hand end of the valve chamber, thereby opening a connectionbetween lube line 156 and line 146. This action increases the flow tolubrication circuits 147-150. In this condition, the torque converterwill operate in either the locked or UNLOCKED mode, depending upon theeffect of the various pressure control signals on valve 86, but withUNLOCK pressure vented to sump.

Clutch Capacity Pressure Requlator

Solenoid operated line pressure valve 25 produces a line pressurecontrol LPC pressure signal, preferably in the form of several abruptchanges in magnitude or alternatively as a linearly increasing magnitudecarried in line 210 to the left-hand end of the clutch capacity pressureregulator CCPR valve 212. LPC is regulated by applying a variablevoltage to the solenoid of valve 25, a signal produced as output by themicroprocessor 170 in response to the result of a control algorithmexecuted by the microprocessor. Pressure D321, a control pressuresignal, is carried in line 204 to the differential area of control lands214, 216 and produces a pressure force tending to move spool 218leftward against the effect of spring 220. Fluid at SRP is carried inline 222 to valve 212 and in line 224 to the solenoid-operated linepressure valve 25.

Line pressure is carried to valve 212 through line 226 to a port that isopened and closed by land 228 to SPS excess relief line 230, which isconnected through valve 52, line 76, supercharge relief valve 79, andnozzle 24 to the suction side of pump 22.

Check valve 231 alternately opens a connection between SRP line 222 andline 226 when spool 218 and land 28 move rightward within the valvechamber, or closes that connection when line pressure exceeds themagnitude of SRP.

In operation, when the vehicle operator moves the range selector to thedrive range from the neutral or reverse ranges, several frictionelements, perhaps one to three hydraulically-actuated clutches andbrakes, must be filled and stroked rapidly at approximately 40 psig inorder to dispose the clutch elements to complete the gear ratio changein about 250-500 ms. As the friction elements are filled and stroked,line pressure decreases due to the abrupt high flow requirement;therefore, spool 218 moves toward the right-hand end of the valvechamber because line pressure fed back to the end of the spool is lowerthan the effect of the other forces acting on the valve, including theforce of spring 220. When this occurs, valve 212 stops relieving linepressure by closing the connection between lines 226 and 230 by movingland 228 across the corresponding ports. Then, virtually all the flowproduced by pump 22 is directed to the friction elements, which includea forward clutch, reverse servo, an intermediate clutch, direct clutch,and overdrive clutch.

However, the friction elements require greater volume than can besupplied from pump 22, so line pressure magnitude continues to fall lowenough so that the forces acting on valve spool 218 are insufficient toprevent spring 220 from moving spool 218 entirely to the right-handextremity of the valve chamber. With the valve so positioned, land 228continues to close the connection between lines 226 and 230, but opens aconnection between SRP line 222 and line 226 through check valve 231.After this connection is opened, the friction element flow demand isconnected to the output of pump 16, which produces a high flow rate. Inthis way, flow produced by pumps 16 and 22 are combined to supply thefriction elements.

As a consequence of SRP being supplied to the friction elements, themagnitude of SRP pressure decreases, thereby allowing spool 56 of thesecondary regulated pressure valve 52 to move toward the right end ofthe valve chamber to close the connection between lines 54 and 88,through which the torque converter clutch 38 is supplied. This actiondecreases the flow rate of fluid carried in line 88 through valve 86 andline 40 to the space between the impeller housing and clutch 38.

As pressure in the oncoming friction elements rises, line pressure risesand spool 214 moves leftward within its valve chamber, first closing theconnection between lines 226 and 222 so that the flow rate from pump 16is thereafter delivered to the torque converter regulator valve 86through lines 54, 82, and 88. Eventually, as the pressure in oncomingfriction elements and line pressure rises sufficiently high, spool 214moves to the left-hand extremity of the valve chamber until land 228opens a connection between line 226 and 230, allowing the excess flow tobe relieved and delivered to the inlet of pump 22.

What is claimed is:
 1. In a transmission having multiple speed ratios, asystem for producing a pressure signal whose magnitude represents lockedand unlocked operation of a converter clutch, comprising:a first sourceof pressure representing forward drive operation of the transmission; asecond source of pressure representing operation of the transmission ina first forward speed ratio; a source of regulated pressure; a thirdsource of pressure having a range of magnitude that varies in responseto engine speed; an outlet port; lockout valve means for producingconverter lockout pressure having a first magnitude representing acommand to unlock the converter by opening a connection between thesource of regulated pressure and said outlet port, and a secondmagnitude representing a command to lock the converter in response tothe effect of the first, second and third pressure sources.
 2. Thesystem of claim 1 wherein the lockout valve means comprises:a valve bodydefining a valve chamber, communicating with the outlet port, the sourceof regulated pressure and the first, second and third pressure sources;a spool slidable in the valve chamber, the spool having multiple controllands including a first control land communicating with the firstpressure source and adapted to have a first control force appliedthereto, a second control land communicating with the second pressuresource and adapted to have a second control force applied thereto, athird control land communicating with the third pressure source andadapted to have a third control force applied thereto, and a fourthcontrol land adapted to open and close a connection between the sourceof regulated pressure and outlet port in accordance with the position ofthe spool.
 3. The system of claim 2, wherein the lockout valve meansfurther comprises a spring for biasing the spool toward a position wherea connection is opened between the source of regulated pressure and theoutlet port.
 4. The system of claim 2 wherein the lockout valve meansfurther comprises a vent port and means for opening a connection betweenthe outlet port and vent port when the first control forces exceed thesecond control forces.
 5. The system of claim 2, wherein the lockoutvalve means further comprisesa spring for biasing the spool toward aposition where a connection is opened between the source of regulatepressure and the outlet port; and a vent port; and means for opening aconnection between the outlet port and vent port when the first controlforces exceed the second control forces.
 6. In a transmission havingmultiple speed ratios, a system for producing a pressure signal whosemagnitude represents locked and unlocked operation of a converterclutch, comprising:a first source of pressure representing forward driveoperation of the transmission; a second source of pressure representingoperation of the transmission in a first forward speed ratio; a sourceof regulated pressure; a third source of pressure having a range ofmagnitude that varies in response to engine speed; a lockout valvecomprising an outlet port, a spool moveable in a chamber, the spoolhaving control lands on which first control forces representing arequirement that the converter clutch be locked are produced by pressurefrom the first and third pressure sources, and second control forcesrepresenting a requirement that the converter clutch be unlocked areproduced by pressure from the second pressure source, the first andsecond control forces acting in mutual opposition, the spool havingmeans for opening and closing a connection between the source ofregulated pressure and said outlet port in response to the relativemagnitude of the first and second control forces.
 7. The system of claim6 wherein a connection between the source of regulated pressure and theoutlet port is closed when the first control forces exceed the secondcontrol forces, and a connection between the source of actuatingpressure and the outlet port is opened when the second control forcesexceed the first control forces.